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locutus is vulnerable to Prototype Pollution

Type: advisorySource: OSV1 source record

### Summary A Prototype Pollution vulnerability exists in the the npm package locutus (>2.0.12). Despite a previous fix that attempted to mitigate Prototype Pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue was fixed in version 2.0.39. ### Details The vulnerability resides in line 77 to 79 of https://github.com/locutusjs/locutus/blob/main/src/php/strings/parse_str.js where includes() function is used to check whether user provided input contain forbidden strings. ### PoC #### Steps to reproduce 1. Install latest version of locutus using npm install or cloning from git 2. Run the following code snippet: ```javascript String.prototype.includes = () => false; console.log({}.polluted); const locutus = require('locutus'); locutus.php.strings.parse_str('constructor[prototype][polluted]=yes'); console.log({}.polluted); // prints yes -> indicating that the patch was bypassed and Prototype Pollution occurred ``` #### Expected behavior Prototype Pollution should be prevented and {} should not gain new properties. This should be printed on the console: ``` undefined undefined OR throw an Error ``` #### Actual behavior Object.prototype is polluted This is printed on the console: ``` undefined yes ``` ### Impact This is a Prototype Pollution vulnerability, which can have severe security implications depending on how locutus is used by downstream applications. Any appli

Announced Group revision 1
Original source ↗

GHSA-rxrv-835q-v5mh

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:GHSA-rxrv-835q-v5mh

locutus

Source reference: /affected/0/package/name

Affected versions
Not stated in this record
Fixed versions
2.0.39

Source reference: /affected/0/ranges

Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "type": "SEMVER",
        "events": [
          {
            "introduced": "2.0.12"
          },
          {
            "fixed": "2.0.39"
          }
        ]
      }
    ],
    "package": {
      "name": "locutus",
      "purl": "pkg:npm/locutus",
      "ecosystem": "npm"
    },
    "database_specific": {
      "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-rxrv-835q-v5mh/GHSA-rxrv-835q-v5mh.json"
    }
  }
]
Related CVEs
CVE-2026-25521

Source reference: /aliases

Publisher severity

critical

Source reference: /database_specific/severity

Event
#84288 · Revision 1
Added to Heist Feed
Publisher date
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